Advances in the field of wireless LAN technology has led to the availability of relatively inexpensive wireless LAN equipment, which, in turn, has resulted in the emergence of publicly accessible wireless LANs (e.g., “hot spots”) at rest stops, cafes, libraries and similar public facilities. Presently, wireless LANs offer users access to a private data network, such as a Corporate Intranet, or a public data network such as the Internet. Few if any publicly accessible wireless LAN's offer any type of telephone service, let alone, wireless telephony service.
Presently, users seeking wireless telephony service typically subscribe to one of many providers of such service. Today's wireless telephony service providers not only offer voice calling but also offer General Packet Radio Service (GPRS) to enable the exchange data packets via a mobile wireless terminal. While GPRS exists in many areas, data transmission rates typically do not exceed 56 Kbps and the costs to wireless network service providers to support this service remain high, making GPRS expensive.
To provide enhanced data communications, efforts are underway to establish new standards for wireless telephony. One such effort is the proposed “Universal Mobile Telecommunications System (UMTS)” standard specified by the 3rd Generation Partnership Project (3GPP) for advanced packet radio service in wireless telephony networks. The UMTS standard proposes transmission rates as high as 2 Mbps. However, the relatively low cost to implement and operate a wireless LAN, as well as the available high bandwidth (usually in excess of 10 Megabits/second) makes the wireless LAN a preferred access mechanism, even as compared to a UMTS network. Given the advantage of lower cost and higher bandwidth, mobile wireless terminal users will often seek to transition to a wireless LAN when such service is available. When wireless LAN service becomes no longer available, the user will transition back to the wireless telephony network.
Access to the wireless telephony network and the wireless LAN both require user identification and verification. From the perspective of the network operator, revenue generation depends on reliable user identification and verification. Absent correct user identification and validation, the network operator will likely be unable to bill for such services. From the user's perspective, identification and verification should occur in a manner that safeguards against identity fraud. Thus, user identification should not occur in a manner that would allow others to make improper use of such information.
Presently, a user seeking access to a wireless telephony network receives a temporary identity, known as a Packet Temporary Mobile Subscriber Identity (P-TMSI). Typically, a Visited Location Register (VLR) attached to Serving GPRS Support Node (SGSN) in the wireless telephony network maintains a copy of the user's P-TMSI. The SGSN maps the P-TMSI to a permanent identity, known as the International Mobile Subscriber Identity (IMSI). To avoid compromising the user's identity, the wireless telephony network will assign the user a different P-TMSI if a long interval has elapsed since a previous identification.
Current wireless LANs lack secure user identification and verification mechanisms. A potential security risk currently exists for users seeking to transition to a wireless LAN from a wireless telephony network.
Thus, there is a need for a technique for protecting the identity of a user when transitioning from one wireless network to another.